This application is a continuation-in-part of U.S. Application Ser. No. 07/324,943, filed Mar. 16, 1990 now U.S. Pat. No. 5,025,619.
1. Field of the Invention
The present invention relates to methods and apparatus for incubating and hatching eggs and more particularly to such methods and apparatus in which trays holding a plurality of eggs are received in a controlled environment for promoting incubation and hatching.
2. Description of the Related Art
Trays for receiving eggs during the incubation process have been in use for many years. Generally speaking, a tray is loaded with freshly-laid eggs and is thereafter received in a rack or the like along with a number of other loaded egg trays. The rack is positioned in a chamber in which the environment, especially temperature and humidity, is controlled to maximize the number of chicks hatched from the eggs. Most, but not all, incubation and hatching methods involve incubating in a first tray which is designed to optimize incubation conditions. Just prior to hatching, the eggs are transferred to a second hatching tray which is designed to accommodate the hatched chicks. Prior art methods include placing the egg on a substantially planar surface in an egg tray.
During incubation, the trays are tilted about a horizontal axis to simulate the same egg movement caused by a hen, through the use of her beak and feet, in a nest. Such movement is important during the incubation process because the chick embryo floats for about the first 14 days of incubation and will stick to the upper surface of the egg and die if the egg is not rotated. On about the 14th day of incubation the chick orients itself with its head in the end of the egg which is tilted upwardly, which should be the large end containing the air cell.
During hatching, which occurs on about the 21st day of incubation, the chick uses its beak to peck through the egg shell along a circle near the air-cell end of the egg and substantially coaxial with the longitudinal axis of the egg. The end of the egg is thus removed and the chick can emerge from the egg.
If the small end of the egg is tilted up when the chick positions itself the chick may malposition with its head in the small end of the egg. When the chick first pips the shell and begins to breathe, it will drown. Even with the chick's head positioned in the air-cell end, if any part of the egg through which the chick must peck is against another object, such as the floor of the egg tray or an adjacent egg, the chick may not be able to peck through the shell and thus dies.
Sometimes the egg tray tilting which must be undertaken during incubation causes the eggs to roll against one another or the egg tray in a manner which may prevent chick hatching as described above. The small end of one egg may ride up onto an adjacent egg or a portion of the tray thereby tilting the longitudinal axis of the egg so that the air-cell end is against the floor of the tray. If the small egg end is higher than the air-cell end, the problems described above may develop.
Prior art egg trays and incubation and hatching methods thus suffer from disadvantages which reduce the yield and quality of hatched chicks.
In addition to the foregoing described problems, the yield of hatched chicks is also reduced as a result of contamination in the incubation chamber. A typical hatchery includes a number of incubation chambers into which portable racks of loaded egg trays are placed for incubation and hatching.
In some methods, the incubation chamber holds eggs at widely varying stages of incubation. The racks supporting the egg trays are serially moved through the incubator with a rack at one end having fresh eggs and with eggs in a rack at the other end being ready to hatch. In such a method the doors to the incubator chamber are opened and closed a number of times during incubation. This permits contamination from chick down and waste to spread from other parts of the hatchery into the chamber.
In other hatchery methods, an incubation chamber is loaded with racks containing fresh eggs and the incubation process is begun. Thus, the doors to the incubation chamber are not opened during incubation, unless it is a system in which the eggs are transferred from incubator trays to hatching trays prior to hatching. Down and waste contamination can, however, enter the chamber when the racks bearing the fresh eggs are first placed in the chamber.